The overall goal of this project is to develop a system for targeted delivery of anthrax toxin inhibitors. Antibiotic treatment currently approved as a post-exposure anthrax therapy is not effective against toxemia, which is induced by anthrax toxins comprising protective antigen (PA) and lethal or edema factors (LF or EF). Several groups develop small molecule inhibitors of toxin enzymatic activity that block toxins inside the cell. However poor membrane permeability, rapid blood clearance, and relatively high working concentrations of these compounds are serious problems that have not been solved so far. To overcome these problems, we propose to encapsulate inhibitors into targeted liposomes for intracellular delivery via anthrax receptors (ANTXR). To test this approach, we will formulate a small-molecule LF inhibitor (IC50 ~ 1 [unreadable]M) into liposome decorated with LFn, a non-toxic fragment of LF with the PA-binding activity. We have recently reported that LFn-liposomes are rapidly internalized via PA-dependent ANTXR-mediated endocytosis, providing new opportunities for targeted intracellular drug delivery. In this part of the project we will establish if LFn-liposomes deliver therapeutically relevant doses of a specific small-molecule LF inhibitor to ANTXR expressing cells and validate protective effect of LFn-liposomes in a toxemia mouse model. The following specific aims are designed to test feasibility of our approach: Specific aim #1. To validate targeting of LFn- liposomes in vivo. Specific aim #2. To optimize LFn-liposomes for efficient delivery of LF inhibitor. Specific aim #3. To establish efficiency of LFn-targeted liposomes in a toxemia mouse model. Accomplishing these specific aims will establish feasibility of using LFn- liposomes for drug delivery. In Phase II we will develop LFn-liposomes with combination of LF and EF inhibitors, validate these liposomes in animal models of anthrax infection, and pre-clinical steps required for IND filing. [unreadable] [unreadable] [unreadable]